THRESHOLDS OF HOMOGENEITY IN TARGETS IN THE LANDSCAPE - RELATIONSHIP WITH REMOTE-SENSING

In the Sahelian context, features making up the landscape are a mixtur e of intermittent elements which can be described not by a single qual itative characteristic but by a range of complementary and, more often , quantitative characteristics. The position of elements in the landsc ape means that their perception poses problems of significance when us ing remote sensing qualitative imagery with a fixed sampling pace. Her e, we indicate how, in our opinion, each target in the environment is defined in relation to two perceptional thresholds, the first one sepa rating from groups of elements of an inferior level, the second one fr om groups of a superior level. We can, therefore, imagine a piling up of levels. The resolution of satellite imagery must, therefore, be com pared with the two limits of each target. In this way, we can ascertai n if it is possible to observe it with such an image and how to do it.